A Multi-Platform Reanalysis of the Kankakee Valley Tornado Cluster on 30 June 2014

Abstract

Two derecho-producing quasi-linear convective systems moved across northeast Illinois and northwest Indiana on the evening of 30 June 2014. Both produced damage across a large area, including a concentrated cluster in the Kankakee River Valley associated with two long-lived and adjacent mesovortices in the second derecho. Post-event surveys of this region revealed a widespread, complex damage pattern and initially documented 14 tornadoes of EF1 rating on the Enhanced Fujita (EF) Scale, along with a swath of damaging nontornadic winds. Later, a number of uncertainties from the original surveys were examined in conjunction with high-resolution satellite imagery not available immediately after the event. Inconsistencies noted during this process led to an intensive reanalysis of the entire cluster using radar data, the original ground and aerial surveys, and the newly available satellite imagery. This new analysis concluded that at least 18 tornadoes impacted the Kankakee Valley, most with a path orientation different from the initial results. This paper details the reassessment process from initial motivation to final results, addresses potential sources of error, and discusses operational considerations stemming from such a prolifically tornadic event.